In one aspect, this invention relates to a process for cracking hydrocarbon-containing feed streams employing catalysts which contain faujacite-type zeolite. In another aspect, this invention relates to a process for cracking gas oils, recycle oils, residua, hydrotreated residua, and the like. In still another aspect, this invention relates to the use of cracking catalysts containing faujacite-type zeolites that have been partially dealuminated. Other objects and advantages will be apparent from the detailed description, drawing and appended claims.
In accordance with this invention, a hydrocarbon-containing feed stream having an initial boiling point (determined according to ASTM D 1160) of at least about 400.degree. F. is contacted with a catalyst composition comprising a faujacite-type zeolite having a unit cell size (unit cell dimension; determined in accordance with ASTM D 3942-80) in the range of from about 24.28 to about 24.48 angstroms and an alkali metal content of less than 0.5 weight percent and being substantially free of iron ions (i.e., containing less than about 0.05 weight-% Fe), under such cracking conditions as to obtain at least one normally liquid (i.e., liquid at 25.degree. C., 1 atm) hydrocarbon-containing product stream having a lower initial boiling point and higher API.sub.60 gravity than said hydrocarbon-containing feed stream.
In a preferred embodiment of this invention, the unit cell size of the faujasite-type zeolite contained in the cracking catalyst composition is in the range of from about 24.31 to about 24.42 angstroms, and the atomic silicon-aluminum ratio in the crystalline framework of said faujasite-type zeolite is in the range of from about 8:1 to about 21:1 (determined by .sup.29 Si solid state nuclear magnetic resonance spectrometry). Preferably, the content of alkali metal (in particular Na) in the faujasite-type zeolite is less than about 0.2 weight percent, and the content of Fe is less than about 0.01 weight percent. Preferred faujasite-type zeolites are Y-zeolites which have been partially dealuminated. Preferred hydrocarbon-containing feed streams comprise gas oils, cracker recycle oils, residua and hydrotreated residua and have preferably a boiling range (ASTM D 1160) of from about 400.degree. to about 1200.degree. F.